(in-package :graph-model)

(defclass num-mixin ()
  ((num :initarg :num :accessor num :initform nil)))

(defmethod change-num ((o num-mixin) newnum)
  (setf (slot-value o 'num) newnum))

(defmethod find-object-from-num (num (objects list) &key (test #'=))
  (find num objects :key #'num :test test))

(defmethod num ((o t))
   nil)